Without a bank account your permitted activities will be restricted. It's just part of the security, identity, and financial policies if you want to use PayPal.
This is not a real answer. It is not specific at all. I have had my account linked to a credit/debit card cince its creation. My account was just as valid. Since Paypal is a target for hackers, I would prefer not to have my bank information in their files. What makes the bank account more valid than the credit/debit card?
Accept payment for an invoice. I never had to do this before. The money was simply in my account and I could leave it or transfer it to my bank account. I only noticed something was wrong when I went to make a purchase and wanted to use some of the payment, but it was not actually showing as available. What makes a bank account more valid than my credit card? What if I did not have a bank account? I do not completely trust Paypal with my banking information. They are a prime target of hackers.
Is this your first time receiving money into your account? If you do not want to add a bank, try adding your SSN to see if that will appease them. There could be an internal reason specific to your account requiring a bank. To find out what that is, if any, you will need to speak to an account specialist.
